CepstralAnalysis (FPScript)

21.09.2021

Computes the cepstrum or its minimum phase reconstruction.

Syntax

CepstralAnalysis(Signal, [ CepstrumType = CEPSTRUM_REAL ], [ FilterLength = 0 ] [ , Peaks ])

 

The syntax of the CepstralAnalysis function consists of the following parts:

Part

Description

Signal

The data to be analyzed. The data must have a constant sampling rate and must not contain void values.

Permitted data structures are data series, data matrix, signal und signal series. All real data types are permitted, except calendar time und time span.

Void values are not permitted in this argument.

For the X component additional restrictions do apply.The values must have a constant positive spacing. Void values are not permitted in this argument.

If the argument is a list, then the function is executed for each element of the list and the result is also a list.

CepstrumType

The cepstrum type to be computed.

The argument CepstrumType can have the following values:

Constant

Meaning

CEPSTRUM_REAL

The real cepstrum: Re{IFFT(ln(|FFT(x)|))}

CEPSTRUM_RECONSTRUCT

The minimum phase reconstruction: Re{IFFT(exp(FFT(L Re{IFFT(ln(|FFT(x)|))})))}

Here, L is a vector containing the "liftering" window.

+ SPECTRUM_PEAKS O

If this constant is added to one of the cepstrum types above, then only peaks in the cepstrum are output. Adding this constant is an alternative to specifying the Peaks argument with a value of 10.

O This constant requires the option Spectral Analysis to be licensed.

Permitted data structures are scalar value. All integral data types are permitted.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

If this argument is omitted, it will be set to the default value CEPSTRUM_REAL.

FilterLength

Specifies the "liftering" window to be applied to the cepstrum while computing a minimum phase reconstruction. This discards all cepstral coefficients above the specified position if it is set between 1 to the size of Signal / 2, or it discards all coefficients below the position defined by the sum of the value if it is set between -1 and minus the size of Signal /2. The default value 0 performs no "liftering".

Permitted data structures are scalar value. All integral data types are permitted.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

If this argument is omitted, it will be set to the default value 0.

Peaks

If specified, then only the peaks of the spectrum are output with the maximum number specified here.

Permitted data structures are scalar value. All integral data types are permitted.

The value must be greater than 1 and less than 100.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

Remarks

Available in

Option Spectral Analysis

Examples

CepstralAnalysis(Signal1)

Calculates the real cepstrum of the signal 'Signal1'. No liftering is performed.

See Also

FFTn Function

Cepstral Analysis - Analysis Object

FFT algorithms

Fourier Spectral Analysis

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